How long to grow a community?

I've been plugging away for about 2 months now trying to grow a small hobby community here on Lemmy. It's doing well, up from 200 to 425 subscribers in the time I've been active.

But, sometimes it feels discouraging. I'm still the only one who posts with any regularity, and I miss the more in-depth discussions I was able to have at the other place. How long, or how many subscribers, does it take for a community to become self-sustaining?

Edit: !geocaching@lemmy.world for anyone curious